Optical color sensor system

ABSTRACT

An optical color sensor system is provided including providing a substrate having an optical sensor therein and forming a passivation layer over the substrate. The passivation layer is planarized and color filters are formed over the passivation layer. A planar transparent layer is formed over the color filters and microlenses are formed on the planar transparent layer over the color filters.

TECHNICAL FIELD

The present invention relates generally to semiconductor systems, andmore particularly to optical sensors.

BACKGROUND ART

Optical color sensors can be found in most of digital camera system. Anincident light is transformed to an electronic signal. Then, theelectronic signal is converted and digitized for an image process andrecorded by an analog/digital converter.

Unfortunately, optical color sensors suffer from color image aberrationsthat distort the true color of the image. These aberrations can becaused by the non-uniformity of pixel-to-pixel color transmissionresulting from the non-uniformity of color resist flow. Some of thepresent solutions are discussed below.

One solution is to apply a low viscosity color resist in a unique spinrecipe onto a standard passivation surface and attempt to optimize thetransmission matching through a photolithography coating process. Thisprocess has inherent drawbacks in that the topographical features of thesurface of the incoming wafer limit the reduction of non-uniformity thatcan be achieved.

Another solution involves inserting a spin on the planarization layerbetween the passivation and the color filter layer. This process suffersfrom integration issues associated with the bondpad interface. Thenon-uniformity of the color filter layer is still on the order of about200 Angstroms peak to trough.

Thus, a need still remains for a system for improving the uniformity ofcolor transmission in optical color sensors. In view of the foregoing,it is increasingly critical that answers be found to these problems.

DISCLOSURE OF THE INVENTION

The present invention provides an optical color sensor system includingproviding a substrate having an optical sensor therein and forming apassivation layer over the substrate. The passivation layer isplanarized and color filters are formed over the passivation layer. Aplanar transparent layer is formed over the color filters andmicrolenses are formed on the planar transparent layer over the colorfilters.

Certain embodiments of the invention have other advantages in additionto or in place of those mentioned or obvious from the above. Theadvantages will become apparent to those skilled in the art from areading of the following detailed description when taken with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an optical color sensor system in anintermediate step of manufacturing after a passivation and depositionstep in accordance with an embodiment of the present invention;

FIG. 2 is the structure of FIG. 1 in a polishing and passivation maskstep in accordance with an embodiment of the present invention;

FIG. 3 is the structure of FIG. 2 in an etching and stripping step inaccordance with an embodiment of the present invention;

FIG. 4 is the structure of FIG. 3 in a coating step in accordance withan embodiment of the present invention;

FIG. 5 is the structure of FIG. 4 in a deposition step of a red colorfilter in accordance with an embodiment of the present invention;

FIG. 6 is the structure of FIG. 5 in a deposition step of a blue colorfilter in accordance with an embodiment of the present invention;

FIG. 7 is the structure of FIG. 6 in a deposition step of a green colorfilter in accordance with an embodiment of the present invention;

FIG. 8 is the structure of FIG. 7 in an etching step in accordance withan embodiment of the present invention;

FIG. 9 is the structure of FIG. 8 in a planarization step in accordancewith an embodiment of the present invention;

FIG. 10 is the structure of FIG. 9 in a formation step in accordancewith an embodiment of the present invention; and

FIG. 11 is a flow chart of a optical color sensor system for fabricatinga optical color sensor in accordance with an embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following description, numerous specific details are given toprovide a thorough understanding of the invention. However, it will beapparent that the invention may be practiced without these specificdetails. In order to avoid obscuring the present invention, somewell-known circuits, system configurations, and process steps are notdisclosed in detail.

Likewise, the drawings showing embodiments of the apparatus/device aresemi-diagrammatic and not to scale and, particularly, some of thedimensions are for the clarity of presentation and are shown greatlyexaggerated in the drawing FIGS.

The term “horizontal” as used herein is defined as a plane parallel tothe conventional plane or surface of a substrate, regardless of itsorientation. The term “vertical” refers to a direction perpendicular tothe horizontal as just defined. Terms, such as , “above”, “below”,“bottom”, “top”, “side” (as in “sidewall”), “higher”, “lower”, “upper”,“over”, and “under”, are defined with respect to the horizontal plane.The term “on” refers to one element being in contact with anotherelement.

The term “processing” as used herein includes deposition of material orphotoresist, patterning, exposure, development, etching, cleaning,and/or removal of the material or photoresist as required in forming adescribed structure.

It has been found that, with new high end mobile camera phones, a yellowdiagonal striation becomes apparent when a picture taken of a monochromebackground is viewed on the phone screen. The source of problem has beendifficult to determine because it does not occur on all phone screens.

After extensive investigation, it has been discovered that the problemis not with the phone screen but on the picture taking end. Even furtherinvestigation revealed that the problem was related to the opticalsensors used to take each pixel of the picture.

However, it was found that the yellow striations would occur with someoptical sensor systems but not with others. This led to the furtherdiscovery that the problem depends upon the location of the opticalcolor sensor chips on a wafer and that the problem will affect ahorrendous 40% to 50% of the chips on a given wafer.

After even further investigation, it was discovered that the problem isassociated with color transmission uniformity through the microlensesthat focus the light on to the optical sensors. It has subsequently beendetermined that microscopic unevenness of the color filters and lensesfor each optical sensor cause the yellow striations.

It was finally discovered that the uniformity of the transmission ofcolor is enhanced through active planarization of a passivation layerprior to application of color filters. The topographical features areeliminated prior to, and during the application of the color filters.

As further described in detail below various layers of transparent orsemi-transparent material are deposited starting with a layer ofencapsulating passivation material is applied over a top metal layer andthen planarized through a process, such as chemical mechanicalplanarization (CMP), prior to application of the color filters. FIGS.1-10 do not illustrate any non-essential color filter topography innon-pixel areas for purposes of clarity.

Referring now to FIG. 1, therein is shown a cross-sectional view of anoptical color sensor system 100 in an intermediate step of manufacturingafter a passivation and deposition step in accordance with an embodimentof the present invention. A substrate 101 contains the optical sensors102 of the optical color sensor system 100.

A metal pad 103 is formed on the substrate 101 and is connected to theoptical sensors. The metal pad 103 is surrounded and covered by a layerof encapsulating passivation material 104. FIG. 1 illustrates an exampleof the metal pad 103 having a thickness of about 6,000 Å. The layer ofencapsulating passivation material 104 may include, for example, silicondioxide or silicon nitride deposited by high density plasma (HDP)deposition. In accordance with one embodiment, the layer ofencapsulating passivation material 104 is deposited to a thickness ofabout 12,000 Å.

A layer of top passivation material 106 is deposited by TEOS depositionon top of the layer of encapsulating passivation material 104. Inaccordance with one embodiment, the layer of top passivation material106 has a thickness of about 12,000 Å.

Referring now to FIG. 2, therein is shown the structure of FIG. 1 in apolishing and passivation mask step in accordance with an embodiment ofthe present invention. The previously deposited layer of top passivationmaterial 106 is uniformly polished back along with a portion of thelayer of encapsulating passivation material 104 until the toppassivation material 106 is completely removed. This leaves a thicknessof the layer of encapsulating passivation material 104 of uniformthickness above the substrate. The thickness is such that about 6,000 Åof material is left above the metal pad 103. A hard mask layer, such asnitride 202, is uniformly deposited on the layer of encapsulatingpassivation material 104.

FIG. 2 illustrates an example of the nitride 202 having a thickness ofabout 5,000 Å. A passivation mask 204 is subsequently deposited on thelayer of nitride 202. The passivation mask 204 is processed to have anopening 206 leaving at least a portion of the top surface of the nitride202 exposed over the metal pad 103 of FIG. 1. In accordance with oneembodiment, the passivation mask 204 includes an L95 resist material(CHRT bondpad layer).

Referring now to FIG. 3, therein is shown the structure of FIG. 2 afteran etching and stripping step in accordance with an embodiment of thepresent invention. The passivation mask 204 is removed and an etchingprocess using the nitride 202 as a hard mask removes an exposed portionof the layer of encapsulating passivation material 104 located above themetal pad 103 to expose the top surface of the metal pad 103.

Referring now to FIG. 4, therein is shown the structure of FIG. 3 in acoating step in accordance with an embodiment of the present invention.A coating layer 402 is deposited on the layer of nitride 202 and the topsurface of the metal pad 103. For illustration purposes, the coatinglayer 402 may have a thickness of about 600 Å. The coating layer 402may, for example, include anti-reflective coating materials.

Referring now to FIG. 5, therein is shown the structure of FIG. 4 in adeposition step of a red color filter in accordance with an embodimentof the present invention. FIG. 5 illustrates a deposition step of a redcolor filter 502, such as, a red color mask. A red color filter 502 isdeposited on a portion of the coating layer 402 that is supported by thelayer of nitride 202. For illustration purposes, the red color filter502 may have a thickness of about 1.0±0.2 μm.

It has been found that the order of deposition of the filters also makesa difference in solving the yellow striation problem. The sequence ofred, blue, and the green filters was used originally but it has beendiscovered that green, red, and then blue filters provides a noticeableimprovement.

Through experimentation, it was found that priming is required toprevent pixel peeling when the blue filter is deposited last. It hasbeen discovered that deposition in the sequence of blue, red, and thengreen filters is not subject to pixel peeling while being comparable togreen, red, and then blue filters.

Referring now to FIG. 6, therein is shown the structure of FIG. 5 in adeposition step of a blue color filter in accordance with an embodimentof the present invention. A blue color filter 602, such as, a blue colormask, is deposited on a portion of the coating layer 402 that issupported by the layer of nitride 202. For illustration purposes, theblue color filter 602 may have a thickness of about 1.0±0.2 μm.

Referring now to FIG. 7, therein is shown the structure of FIG. 6 in adeposition step of a green color filter in accordance with an embodimentof the present invention. A green color filter 702 such as, a greencolor mask, is deposited on a portion of the coating layer 402 that issupported by the layer of nitride 202. FIG. 7 illustrates an examplewhere the green color filter 702 is deposited adjacently to the bluecolor filter 602 and/or the red color filter 502. For illustrationpurposes, the green color filter 702 may have a thickness of about1.1±0.2 μm.

Referring now to FIG. 8, therein is shown the structure of FIG. 7 in anetching step in accordance with an embodiment of the present invention.An exposed portion of the coating layer 402 located above adjacent themetal pad 103 is removed or etched away during the etching step. Theetching process also removes a thickness of less than 1,000 Å from thered color filter 502, the blue color filter 602, and the green colorfilter 702.

Referring now to FIG. 9, therein is shown the structure of FIG. 8 in aplanarization step in accordance with an embodiment of the presentinvention. A layer of planar material 902 is uniformly deposited on thetop surface of the red color filter 502, the blue color filter 602, andthe green color filter 702 to form a planar top surface. In accordancewith one embodiment, the planar transparent layer 902 has a thickness ofabout 0.95±0.2 μm.

Referring now to FIG. 10, therein is shown the structure of FIG. 9 in aformation step in accordance with an embodiment of the presentinvention. A microlens 1002 is formed on top of the planar transparentlayer 902. FIG. 10 illustrates a plurality of microlenses where eachmicrolens 1002 is adjacent to the red color filter 502, the blue colorfilter 602, and the green color filter 702. In accordance with oneembodiment, each microlens 1002 has a thickness of about 1.0±0.1 μm. Thespace between each microlens 1002 may range from about 0.2 μm to about0.5 μm. Each microlens 1002 may have a horizontal dimension ranging fromabout 5.3 μm to about 5.4 μm.

Referring now to FIG. 11, therein is shown a flow chart of an opticalcolor sensor system 1100 for manufacturing the optical color sensorsystem 100 in accordance with an embodiment of the present invention.The system 1100 includes providing a substrate having an optical sensortherein in a block 1102; forming a passivation layer over the substratein a block 1104; planarizing the passivation layer in a block 1106;forming color filters over the passivation layer in a block 1108;forming a planar transparent layer over the color filters in a block1110; and forming microlenses on the planar transparent layer over thecolor filters in a block 1112.

In greater detail, a system to optical sensor color transmissionuniformity enhancement by active planarization of passivation, accordingto an embodiment of the present invention, is performed as follows:

-   -   1. providing the metal pad 103, encapsulating the metal pad 103        with the layer of encapsulating passivation material 104, and        depositing the layer of top passivation material 106 on top of        the layer of encapsulating passivation material 104. (FIG. 1)    -   2. polishing back the layer of top passivation material 106,        depositing the layer of nitride 202 on the layer of        encapsulating passivation material 104, depositing the        passivation mask 204 on the layer of nitride 202. (FIG. 2)    -   3. etching the passivation mask 204 and the exposed portion of        the layer of encapsulating passivation material 104. (FIG. 3)    -   4. depositing the coating layer 402 on the layer of nitride 202        and on the metal pad 103. (FIG. 4)    -   5. depositing the red color filter 502 on the coating layer 402.        (FIG. 4)    -   6. depositing the blue color filter 602 on the coating layer        402. (FIG. 6)    -   7. depositing the green color filter 702 on the coating layer        402. (FIG. 7)    -   8. etching the exposed portion of the coating layer 402. (FIG.        8)    -   9. depositing the planar transparent layer 902 on the red color        filter 502, the blue color filter 602, and the green color        filter 702. (FIG. 9)    -   10. forming a microlens 1002 on the planar transparent layer        902. (FIG. 10)

It has been discovered that the present invention thus has numerousadvantages.

An aspect is that by actively planarizing the semiconductor passivationsurface prior to and during color filter resist dispense,topographically-induced flow non-uniformities are significantly reducedor eliminated. This leads to significantly enhanced pixel colortransmission uniformity through a reduction in fluid mechanicalresistance during color resist dispense. This color filternon-uniformity is on the order of about 20 Å peak to trough,(representing an order of magnitude reduction in non-uniformity over theprior schemes).

Yet another aspect of the present invention is that it valuably supportsand services the historical trend of reducing costs, simplifyingsystems, and increasing performance.

These and other valuable aspects of the present invention consequentlyfurther the state of the technology to at least the next level.

The resulting processes and configurations are straightforward,cost-effective, uncomplicated, highly versatile and effective, can beimplemented by adapting known technologies, and are thus readily suitedfor efficiently and economically manufacturing large die IC packageddevices.

While the invention has been described in conjunction with a specificbest mode, it is to be understood that many alternatives, modifications,and variations will be apparent to those skilled in the art in light ofthe aforegoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications, and variations that fall within thescope of the included claims. All matters hithertofore set forth hereinor shown in the accompanying drawings are to be interpreted in anillustrative and non-limiting sense.

1. An optical color sensor system comprising: providing a substratehaving an optical sensor therein; forming a passivation layer over thesubstrate; planarizing the passivation layer; forming color filters overthe passivation layer; forming a planar transparent layer over the colorfilters; and forming microlenses on the planar transparent layer overthe color filters.
 2. The system as claimed in claim 1 furthercomprising: forming the passivation layer further comprises: depositingan encapsulating passivation layer, and forming a top passivation layeron the encapsulating passivation layer; and planarizing the passivationlayer further comprises: planarizing the top passivation layer to removethe top passivation layer and a portion of the encapsulating passivationlayer.
 3. The system as claimed in claim 1 further comprising: providinga metal pad on the substrate connected to the optical sensor; formingthe passivation layer further comprises: encapsulating the metal pad inan encapsulating passivation layer, and forming a top passivation layeron the encapsulating passivation layer; and planarizing the passivationlayer further comprises: planarizing the top passivation layer to removethe top passivation layer and a portion of the encapsulating passivationlayer.
 4. The system as claimed in claim 1 further comprising: providinga metal pad on the substrate connected to the optical sensor; formingthe passivation layer further comprises: depositing a hard mask layer onthe passivation layer, forming a passivation mask on the hard masklayer, processing the hard mask layer using the passivation mask, andprocessing the passivation layer using the hard mask layer; coating themetal pad and the hard mask layer with a coating layer; removing thecoating layer from the metal pad; and forming the color filters formsthe color filters on the coating layer.
 5. The system as claimed inclaim 1 further comprising: depositing a coating layer over thepassivation layer; forming the color filters further includes:depositing a red color filter, a blue color filter, and a green colorfilter on the coating layer; depositing a planar transparent layer onthe color filters; and forming the microlenses further comprises:forming the microlenses on the coating layer over the red color filter,the blue color filter, and the green color filter.
 6. An optical colorsensor system comprising: providing a substrate having an optical sensortherein; depositing a passivation layer over the substrate; planarizingthe passivation layer; depositing color filters over the passivationlayer after planarization; depositing a planar transparent layer on andover the color filters; and forming microlenses on the planartransparent layer over each of the color filters.
 7. The system asclaimed in claim 6 further comprising: depositing the passivation layerfurther comprises: depositing an encapsulating passivation layer on thesubstrate, and forming a top passivation layer on the encapsulatingpassivation layer; and planarizing the passivation layer furthercomprises: polishing the top passivation layer to remove the toppassivation layer and a portion of the encapsulating passivation layer.8. The system as claimed in claim 6 further comprising: providing ametal pad on the substrate connected to the optical sensor; depositingthe passivation layer further comprises: encapsulating the metal pad inan encapsulating passivation layer, the encapsulating passivation layerincludes a material selected from silicon dioxide, silicon nitride, analloy thereof, a compound thereof, and a combination thereof, anddepositing a top passivation layer on the encapsulating passivationlayer; and planarizing the passivation layer further comprises:polishing the top passivation layer to remove the top passivation layerand a portion of the encapsulating passivation layer, the polishing backof the encapsulating passivation layer to a thickness of about 6,000 Åover the metal pad.
 9. The system as claimed in claim 6 furthercomprising: providing a metal pad on the substrate connected to theoptical sensor; depositing the passivation layer further comprises:depositing a hard mask layer on the passivation layer, forming apassivation mask on the hard mask layer, processing the hard mask layerusing the passivation mask, and processing the passivation layer usingthe hard mask layer; coating the metal pad and the hard mask layer witha bottom anti-reflective coating; removing the coating layer from themetal pad; and depositing the color filters form the color filters onthe coating layer.
 10. The system as claimed in claim 6 furthercomprising: depositing a coating layer over the passivation layer; anddepositing the color filters further includes: depositing a red colorfilter, a blue color filter, and a green color filter on the coatinglayer; depositing a planar transparent layer on the color filters; andforming the microlenses further comprises: forming the microlenses onthe planar transparent layer over the red color filter, the blue colorfilter, and the green color filter.
 11. An optical color sensor systemcomprising: a substrate; an optical sensor in the substrate; aplanarized passivation layer over the substrate; color filters over thepassivation layer; a planar transparent layer over the color filters;and microlenses on the planar transparent layer over the color filters.12. The system as claimed in claim 11 further comprising: thepassivation layer further comprises: an encapsulating passivation layer.13. The system as claimed in claim 11 further comprising: a metal pad onthe substrate connected to the optical sensor; the passivation layerfurther comprises: an encapsulating passivation layer encapsulating themetal pad with the top surface of the metal pad exposed.
 14. The systemas claimed in claim 11 further comprising: a metal pad on the substrateconnected to the optical sensor; the passivation layer furthercomprises: an encapsulating passivation layer, and a hard mask layer onthe encapsulating passivation layer; a coating layer on the hard masklayer with the top surface of the metal pad exposed; and the colorfilters formed on the coating layer.
 15. The system as claimed in claim11 further comprising: a coating layer over the passivation layer; thecolor filters further include: a red color filter, a blue color filter,and a green color filter on the coating layer; a planar transparentlayer on the color filters; and the microlenses further comprise: themicrolenses on the coating layer over the red color filter, the bluecolor filter, and the green color filter.
 16. The system as claimed inclaim 11 comprising: the substrate having an optical sensor therein fordetecting light thereon; the passivation layer over the substrateproviding a planarized surface; the color filters over the planarizedsurface of the passivation layer; the planar transparent layer on andover the color filters; and the microlenses on and over the planartransparent layer over each of the color filters.
 17. The system asclaimed in claim 16 further comprising: the passivation layer furthercomprises an encapsulating passivation layer on the substrate, theencapsulating passivation layer characterized in having a planar topsurface.
 18. The system as claimed in claim 16 further comprising: ametal pad on the substrate connected to the optical sensor; and thepassivation layer further comprises an encapsulating passivation layerencapsulating the metal pad of a thickness of about 6,000 Å over themetal pad.
 19. The system as claimed in claim 16 further comprising: ametal pad on the substrate connected to the optical sensor; thepassivation layer further comprises: a hard mask layer on thepassivation layer, and a passivation mask on the hard mask layer; acoating layer of a bottom anti-reflective coating on the hard masklayer; and the color filters formed on the coating layer.
 20. The systemas claimed in claim 16 further comprising: a coating layer over thepassivation layer; the color filters further includes a red colorfilter, a blue color filter, and a green color filter on the coatinglayer; a planar transparent layer on the color filters; and themicrolens further comprises the microlenses formed on the coating layerover the red color filter, the blue color filter, and the green colorfilter.